1/*
2 * This program is free software; you can redistribute it and/or modify
3 * it under the terms of the GNU General Public License as published by
4 * the Free Software Foundation; either version 2 of the License, or
5 * (at your option) any later version.
6 *
7 * This program is distributed in the hope that it will be useful,
8 * but WITHOUT ANY WARRANTY; without even the implied warranty of
9 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
10 * GNU General Public License for more details.
11 *
12 * You should have received a copy of the GNU General Public License
13 * along with this program; if not, write to the Free Software
14 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
15 *
16 * Copyright (C) IBM Corporation, 2005
17 *               Jeff Muizelaar, 2006, 2007
18 *               Pekka Paalanen, 2008 <pq@iki.fi>
19 *
20 * Derived from the read-mod example from relay-examples by Tom Zanussi.
21 */
22
23#define pr_fmt(fmt) "mmiotrace: " fmt
24
25#define DEBUG 1
26
27#include <linux/module.h>
28#include <linux/debugfs.h>
29#include <linux/slab.h>
30#include <linux/uaccess.h>
31#include <linux/io.h>
32#include <linux/kallsyms.h>
33#include <asm/pgtable.h>
34#include <linux/mmiotrace.h>
35#include <asm/e820.h> /* for ISA_START_ADDRESS */
36#include <linux/atomic.h>
37#include <linux/percpu.h>
38#include <linux/cpu.h>
39
40#include "pf_in.h"
41
42struct trap_reason {
43	unsigned long addr;
44	unsigned long ip;
45	enum reason_type type;
46	int active_traces;
47};
48
49struct remap_trace {
50	struct list_head list;
51	struct kmmio_probe probe;
52	resource_size_t phys;
53	unsigned long id;
54};
55
56/* Accessed per-cpu. */
57static DEFINE_PER_CPU(struct trap_reason, pf_reason);
58static DEFINE_PER_CPU(struct mmiotrace_rw, cpu_trace);
59
60static DEFINE_MUTEX(mmiotrace_mutex);
61static DEFINE_SPINLOCK(trace_lock);
62static atomic_t mmiotrace_enabled;
63static LIST_HEAD(trace_list);		/* struct remap_trace */
64
65/*
66 * Locking in this file:
67 * - mmiotrace_mutex enforces enable/disable_mmiotrace() critical sections.
68 * - mmiotrace_enabled may be modified only when holding mmiotrace_mutex
69 *   and trace_lock.
70 * - Routines depending on is_enabled() must take trace_lock.
71 * - trace_list users must hold trace_lock.
72 * - is_enabled() guarantees that mmio_trace_{rw,mapping} are allowed.
73 * - pre/post callbacks assume the effect of is_enabled() being true.
74 */
75
76/* module parameters */
77static unsigned long	filter_offset;
78static bool		nommiotrace;
79static bool		trace_pc;
80
81module_param(filter_offset, ulong, 0);
82module_param(nommiotrace, bool, 0);
83module_param(trace_pc, bool, 0);
84
85MODULE_PARM_DESC(filter_offset, "Start address of traced mappings.");
86MODULE_PARM_DESC(nommiotrace, "Disable actual MMIO tracing.");
87MODULE_PARM_DESC(trace_pc, "Record address of faulting instructions.");
88
89static bool is_enabled(void)
90{
91	return atomic_read(&mmiotrace_enabled);
92}
93
94static void print_pte(unsigned long address)
95{
96	unsigned int level;
97	pte_t *pte = lookup_address(address, &level);
98
99	if (!pte) {
100		pr_err("Error in %s: no pte for page 0x%08lx\n",
101		       __func__, address);
102		return;
103	}
104
105	if (level == PG_LEVEL_2M) {
106		pr_emerg("4MB pages are not currently supported: 0x%08lx\n",
107			 address);
108		BUG();
109	}
110	pr_info("pte for 0x%lx: 0x%llx 0x%llx\n",
111		address,
112		(unsigned long long)pte_val(*pte),
113		(unsigned long long)pte_val(*pte) & _PAGE_PRESENT);
114}
115
116/*
117 * For some reason the pre/post pairs have been called in an
118 * unmatched order. Report and die.
119 */
120static void die_kmmio_nesting_error(struct pt_regs *regs, unsigned long addr)
121{
122	const struct trap_reason *my_reason = &get_cpu_var(pf_reason);
123	pr_emerg("unexpected fault for address: 0x%08lx, last fault for address: 0x%08lx\n",
124		 addr, my_reason->addr);
125	print_pte(addr);
126	print_symbol(KERN_EMERG "faulting IP is at %s\n", regs->ip);
127	print_symbol(KERN_EMERG "last faulting IP was at %s\n", my_reason->ip);
128#ifdef __i386__
129	pr_emerg("eax: %08lx   ebx: %08lx   ecx: %08lx   edx: %08lx\n",
130		 regs->ax, regs->bx, regs->cx, regs->dx);
131	pr_emerg("esi: %08lx   edi: %08lx   ebp: %08lx   esp: %08lx\n",
132		 regs->si, regs->di, regs->bp, regs->sp);
133#else
134	pr_emerg("rax: %016lx   rcx: %016lx   rdx: %016lx\n",
135		 regs->ax, regs->cx, regs->dx);
136	pr_emerg("rsi: %016lx   rdi: %016lx   rbp: %016lx   rsp: %016lx\n",
137		 regs->si, regs->di, regs->bp, regs->sp);
138#endif
139	put_cpu_var(pf_reason);
140	BUG();
141}
142
143static void pre(struct kmmio_probe *p, struct pt_regs *regs,
144						unsigned long addr)
145{
146	struct trap_reason *my_reason = &get_cpu_var(pf_reason);
147	struct mmiotrace_rw *my_trace = &get_cpu_var(cpu_trace);
148	const unsigned long instptr = instruction_pointer(regs);
149	const enum reason_type type = get_ins_type(instptr);
150	struct remap_trace *trace = p->private;
151
152	/* it doesn't make sense to have more than one active trace per cpu */
153	if (my_reason->active_traces)
154		die_kmmio_nesting_error(regs, addr);
155	else
156		my_reason->active_traces++;
157
158	my_reason->type = type;
159	my_reason->addr = addr;
160	my_reason->ip = instptr;
161
162	my_trace->phys = addr - trace->probe.addr + trace->phys;
163	my_trace->map_id = trace->id;
164
165	/*
166	 * Only record the program counter when requested.
167	 * It may taint clean-room reverse engineering.
168	 */
169	if (trace_pc)
170		my_trace->pc = instptr;
171	else
172		my_trace->pc = 0;
173
174	/*
175	 * XXX: the timestamp recorded will be *after* the tracing has been
176	 * done, not at the time we hit the instruction. SMP implications
177	 * on event ordering?
178	 */
179
180	switch (type) {
181	case REG_READ:
182		my_trace->opcode = MMIO_READ;
183		my_trace->width = get_ins_mem_width(instptr);
184		break;
185	case REG_WRITE:
186		my_trace->opcode = MMIO_WRITE;
187		my_trace->width = get_ins_mem_width(instptr);
188		my_trace->value = get_ins_reg_val(instptr, regs);
189		break;
190	case IMM_WRITE:
191		my_trace->opcode = MMIO_WRITE;
192		my_trace->width = get_ins_mem_width(instptr);
193		my_trace->value = get_ins_imm_val(instptr);
194		break;
195	default:
196		{
197			unsigned char *ip = (unsigned char *)instptr;
198			my_trace->opcode = MMIO_UNKNOWN_OP;
199			my_trace->width = 0;
200			my_trace->value = (*ip) << 16 | *(ip + 1) << 8 |
201								*(ip + 2);
202		}
203	}
204	put_cpu_var(cpu_trace);
205	put_cpu_var(pf_reason);
206}
207
208static void post(struct kmmio_probe *p, unsigned long condition,
209							struct pt_regs *regs)
210{
211	struct trap_reason *my_reason = &get_cpu_var(pf_reason);
212	struct mmiotrace_rw *my_trace = &get_cpu_var(cpu_trace);
213
214	/* this should always return the active_trace count to 0 */
215	my_reason->active_traces--;
216	if (my_reason->active_traces) {
217		pr_emerg("unexpected post handler");
218		BUG();
219	}
220
221	switch (my_reason->type) {
222	case REG_READ:
223		my_trace->value = get_ins_reg_val(my_reason->ip, regs);
224		break;
225	default:
226		break;
227	}
228
229	mmio_trace_rw(my_trace);
230	put_cpu_var(cpu_trace);
231	put_cpu_var(pf_reason);
232}
233
234static void ioremap_trace_core(resource_size_t offset, unsigned long size,
235							void __iomem *addr)
236{
237	static atomic_t next_id;
238	struct remap_trace *trace = kmalloc(sizeof(*trace), GFP_KERNEL);
239	/* These are page-unaligned. */
240	struct mmiotrace_map map = {
241		.phys = offset,
242		.virt = (unsigned long)addr,
243		.len = size,
244		.opcode = MMIO_PROBE
245	};
246
247	if (!trace) {
248		pr_err("kmalloc failed in ioremap\n");
249		return;
250	}
251
252	*trace = (struct remap_trace) {
253		.probe = {
254			.addr = (unsigned long)addr,
255			.len = size,
256			.pre_handler = pre,
257			.post_handler = post,
258			.private = trace
259		},
260		.phys = offset,
261		.id = atomic_inc_return(&next_id)
262	};
263	map.map_id = trace->id;
264
265	spin_lock_irq(&trace_lock);
266	if (!is_enabled()) {
267		kfree(trace);
268		goto not_enabled;
269	}
270
271	mmio_trace_mapping(&map);
272	list_add_tail(&trace->list, &trace_list);
273	if (!nommiotrace)
274		register_kmmio_probe(&trace->probe);
275
276not_enabled:
277	spin_unlock_irq(&trace_lock);
278}
279
280void mmiotrace_ioremap(resource_size_t offset, unsigned long size,
281						void __iomem *addr)
282{
283	if (!is_enabled()) /* recheck and proper locking in *_core() */
284		return;
285
286	pr_debug("ioremap_*(0x%llx, 0x%lx) = %p\n",
287		 (unsigned long long)offset, size, addr);
288	if ((filter_offset) && (offset != filter_offset))
289		return;
290	ioremap_trace_core(offset, size, addr);
291}
292
293static void iounmap_trace_core(volatile void __iomem *addr)
294{
295	struct mmiotrace_map map = {
296		.phys = 0,
297		.virt = (unsigned long)addr,
298		.len = 0,
299		.opcode = MMIO_UNPROBE
300	};
301	struct remap_trace *trace;
302	struct remap_trace *tmp;
303	struct remap_trace *found_trace = NULL;
304
305	pr_debug("Unmapping %p.\n", addr);
306
307	spin_lock_irq(&trace_lock);
308	if (!is_enabled())
309		goto not_enabled;
310
311	list_for_each_entry_safe(trace, tmp, &trace_list, list) {
312		if ((unsigned long)addr == trace->probe.addr) {
313			if (!nommiotrace)
314				unregister_kmmio_probe(&trace->probe);
315			list_del(&trace->list);
316			found_trace = trace;
317			break;
318		}
319	}
320	map.map_id = (found_trace) ? found_trace->id : -1;
321	mmio_trace_mapping(&map);
322
323not_enabled:
324	spin_unlock_irq(&trace_lock);
325	if (found_trace) {
326		synchronize_rcu(); /* unregister_kmmio_probe() requirement */
327		kfree(found_trace);
328	}
329}
330
331void mmiotrace_iounmap(volatile void __iomem *addr)
332{
333	might_sleep();
334	if (is_enabled()) /* recheck and proper locking in *_core() */
335		iounmap_trace_core(addr);
336}
337
338int mmiotrace_printk(const char *fmt, ...)
339{
340	int ret = 0;
341	va_list args;
342	unsigned long flags;
343	va_start(args, fmt);
344
345	spin_lock_irqsave(&trace_lock, flags);
346	if (is_enabled())
347		ret = mmio_trace_printk(fmt, args);
348	spin_unlock_irqrestore(&trace_lock, flags);
349
350	va_end(args);
351	return ret;
352}
353EXPORT_SYMBOL(mmiotrace_printk);
354
355static void clear_trace_list(void)
356{
357	struct remap_trace *trace;
358	struct remap_trace *tmp;
359
360	/*
361	 * No locking required, because the caller ensures we are in a
362	 * critical section via mutex, and is_enabled() is false,
363	 * i.e. nothing can traverse or modify this list.
364	 * Caller also ensures is_enabled() cannot change.
365	 */
366	list_for_each_entry(trace, &trace_list, list) {
367		pr_notice("purging non-iounmapped trace @0x%08lx, size 0x%lx.\n",
368			  trace->probe.addr, trace->probe.len);
369		if (!nommiotrace)
370			unregister_kmmio_probe(&trace->probe);
371	}
372	synchronize_rcu(); /* unregister_kmmio_probe() requirement */
373
374	list_for_each_entry_safe(trace, tmp, &trace_list, list) {
375		list_del(&trace->list);
376		kfree(trace);
377	}
378}
379
380#ifdef CONFIG_HOTPLUG_CPU
381static cpumask_var_t downed_cpus;
382
383static void enter_uniprocessor(void)
384{
385	int cpu;
386	int err;
387
388	if (downed_cpus == NULL &&
389	    !alloc_cpumask_var(&downed_cpus, GFP_KERNEL)) {
390		pr_notice("Failed to allocate mask\n");
391		goto out;
392	}
393
394	get_online_cpus();
395	cpumask_copy(downed_cpus, cpu_online_mask);
396	cpumask_clear_cpu(cpumask_first(cpu_online_mask), downed_cpus);
397	if (num_online_cpus() > 1)
398		pr_notice("Disabling non-boot CPUs...\n");
399	put_online_cpus();
400
401	for_each_cpu(cpu, downed_cpus) {
402		err = cpu_down(cpu);
403		if (!err)
404			pr_info("CPU%d is down.\n", cpu);
405		else
406			pr_err("Error taking CPU%d down: %d\n", cpu, err);
407	}
408out:
409	if (num_online_cpus() > 1)
410		pr_warning("multiple CPUs still online, may miss events.\n");
411}
412
413static void leave_uniprocessor(void)
414{
415	int cpu;
416	int err;
417
418	if (downed_cpus == NULL || cpumask_weight(downed_cpus) == 0)
419		return;
420	pr_notice("Re-enabling CPUs...\n");
421	for_each_cpu(cpu, downed_cpus) {
422		err = cpu_up(cpu);
423		if (!err)
424			pr_info("enabled CPU%d.\n", cpu);
425		else
426			pr_err("cannot re-enable CPU%d: %d\n", cpu, err);
427	}
428}
429
430#else /* !CONFIG_HOTPLUG_CPU */
431static void enter_uniprocessor(void)
432{
433	if (num_online_cpus() > 1)
434		pr_warning("multiple CPUs are online, may miss events. "
435			   "Suggest booting with maxcpus=1 kernel argument.\n");
436}
437
438static void leave_uniprocessor(void)
439{
440}
441#endif
442
443void enable_mmiotrace(void)
444{
445	mutex_lock(&mmiotrace_mutex);
446	if (is_enabled())
447		goto out;
448
449	if (nommiotrace)
450		pr_info("MMIO tracing disabled.\n");
451	kmmio_init();
452	enter_uniprocessor();
453	spin_lock_irq(&trace_lock);
454	atomic_inc(&mmiotrace_enabled);
455	spin_unlock_irq(&trace_lock);
456	pr_info("enabled.\n");
457out:
458	mutex_unlock(&mmiotrace_mutex);
459}
460
461void disable_mmiotrace(void)
462{
463	mutex_lock(&mmiotrace_mutex);
464	if (!is_enabled())
465		goto out;
466
467	spin_lock_irq(&trace_lock);
468	atomic_dec(&mmiotrace_enabled);
469	BUG_ON(is_enabled());
470	spin_unlock_irq(&trace_lock);
471
472	clear_trace_list(); /* guarantees: no more kmmio callbacks */
473	leave_uniprocessor();
474	kmmio_cleanup();
475	pr_info("disabled.\n");
476out:
477	mutex_unlock(&mmiotrace_mutex);
478}
479